Welders and others wear welding helmets, face shielding devices, etc., to protect themselves from strong ultraviolet, visible and/or infrared light rays that are emitted from a welding arc. As used herein light may mean electromagnetic energy in the ultraviolet, visible and/or infrared ranges. Welding helmets also provide a protective barrier between the welder and the welding arc fumes, heat, hot metal spatter, sparks, and possibly other flying debris.
An example of a welding helmet includes an outside shell with a viewing port, a mounting head band, and means for mounting a welding lens in the viewing port such as a viewing port filter plate retainer mechanism. The viewing port may include a darkened piece of glass, plastic or other material often referred to as a lens or as a welding lens, the object of which is to permit viewing of a welding operation while protecting the eyes of the welder from the ultraviolet, visible, and/or infrared light occurring during a welding operation. The lens may be of the automatic type which darkens to block such light during welding and which lightens to transmit more light when welding is not occurring. Examples of such automatic welding lenses are disclosed in U.S. Pat. Nos. 5,074,647, 5,208,688; 5,248,880; and 5,252,817; the entire disclosures of which are hereby incorporated by reference. Other types of automatic welding lenses and fixed welding lenses may be used in welding helmets, as is known.
Various mounting headbands have been used to mount a welding helmet, etc. on the head of a person. Modern headbands are adjustable to head size and some are attached to and mounted on a welding helmet to permit relative pivoting movement to allow the helmet to be opened and/or to allow the helmet to be placed comfortably and securely on the head. A pivoting connection between the mounting headband and a welding face shield device, for example, also is used to enable tilting of the face shield between a down position in front of the face and an up position above the top of the head.
Welding helmet shells that are currently made are constructed primarily either of thermoplastic injection molded resins or blends; formed fiberglass or sheet resin materials; or pattern cut and fastened vulcanized fiberboard. These materials have been suitable for welding helmet construction because they offer adequate temperature and impact resistance, but they all are relatively heavy, usually weighing more than 0.5 pounds for the shell only. It would be desirable to reduce the weight of a welding helmet or like device. It also would be desirable to improve the resistance of a welding helmet to hot metal spatter and to sparks and to improve the durability and ability to withstand severe impacts.
Composite material as referred to herein means, for example, a material created from a fiber (or reinforcement) and an appropriate matrix material in order to provide, preferably to maximize, specific performance properties. The constituents do not dissolve or merge completely but retain their identities as they act in concert. Examples of composite material in the context of the present invention include woven fiber, such as that sold under the trademark Kevlar, embedded in a resin matrix, such as epoxy, polyimide, or polyester or other matrix materials. Kevlar material is an aramid fiber sold by DuPont. Such woven fiber and resin may form a single ply or a multiple ply (laminate) structure. The composite material used has characteristics enabling it to be molded, for example, in the manner described herein. Kevlar composite material that includes a woven fiber of Kevlar and a resin or other matrix, adhesive or support type material usually was not able to be conveniently molded in the past to form structures, such as welding helmets. For example, stiffness of the composite material and the relatively poor bonding with the resin, etc., made molding of such structures relatively difficult or impossible. It would be desirable to mold such structures from composite material, such as Kevlar material, to facilitate, expedite and reduce the cost of making such structure from such composite material and/or to enable the manufacturing of such structures from such composite material. Other exemplary composite materials are described below.
Although composite materials have a number of advantageous characteristics, such as light impermeability, especially when including a dye or other light blocking material, light weight, temperature resistance, and durability, other characteristics, several of which are mentioned below, make them undesirable for use in welding helmets, hard hats, other face shielding devices, and other devices where structural integrity or continuity of shape are required. The cost to obtain the composite material thickness that is required for strength of the particular object is often prohibitive for their use. Such cost may be due to the amount of material required for structural integrity, stiffness, and impermeability. For example, bullet proof vests, rocket nozzles and rocket fins/control surfaces made of Kevlar material usually are formed of several layers that are laid up (placed in layers) in a mold, and this labor intensive process is time consuming and expensive. Also, such laid up material often must cure in the mold for a relatively long time, sometimes an hour or more, which is time consuming and expensive.
It would be desirable to increase the utility of such composite materials, especially by making them easily used in devices which require such structural integrity. Examples of such devices may well be welding helmets, hard hats, face shielding devices, and/or other devices used for protective purposes, such as those mentioned above, and/or for other purposes.
Furthermore, it is difficult and sometimes not possible to form mechanical details or features in composite materials. An exemplary mechanical feature may be a support device, a support opening, and/or a threaded opening structure for connecting a mounting headband to a welding helmet shell. For example, due to the lack of rigidity and/or the relative impenetrability of composite material of Kevlar and resin it is difficult to form such details or features, and such details and features may not hold up during use of the structure. It would be desirable to provide in a device that uses such composite material, mechanical details for fastening, reinforcement, and/or other purposes.
Composite materials also tend to have relatively ragged or unsmooth edges, and various techniques have been used in the past to finish those edges to provide a smooth edge. Rough edges are undesirable because they can help cause the breakage of the composite panel upon side impact. It would be desirable to facilitate finishing such edges to provide smooth surfaces that are less likely to encounter breakage as well as to cause a potential hazard to the user.
A disadvantage of using a dyed material, such as fiberglass and a dyed resin as a welding helmet is the light permeability of the dyed material. The dye absorbs light but, may not block all transmission. It would be desirable to increase light blocking effectiveness of a welding helmet. Various of the above difficulties and/or disadvantages to use Kevlar composite material or the like are addressed in copending U.S. patent application Ser. No. 08/270,633. In that application is disclosed a structure of composite material and a plastic injection molded frame insert molded to the composite material. A complicating factor in such insert molding method can be shrinkage of the molded plastic material, which may distort the shape of the molded structure, e.g., welding helmet, and/or reduce strength characteristics. Another such factor may be knit lines where plastic flouring from different directions comes together and "knits"; sometimes structural weakness may occur and lessen lines. Although close or accurate control of the molded material, design and/or molding conditions, e.g., temperature, flow rates, pressure, etc., may alleviate these difficulties, it would be desirable to avoid them without the need for such close control of insert molding material and process.
Another possible disadvantage of such insert molding technique of the mentioned patent application is the added weight of the molded frame or rib members relative to the lighter weight composite material. It would be desirable to minimize weight of a welding helmet.